The present invention relates generally to fuel delivery systems and more specifically to a fuel delivery system that can reduce fuel vapor in direct injection applications.
Known fuel injection systems allow control over the amount of fuel entering the intake system of an engine, which improves engine efficiency and vehicle performance. Fuel injection has become standard on four-wheeled vehicles and a growing number of two-wheeled vehicles. The reasons go beyond the potential performance gains offered by fuel injection. Increasing concerns over vehicle emissions and depleted fossil fuels have made fuel injection technology a required component for vehicle manufacturers hoping to comply with clean air and other standards.
Direct injection systems are based on the concept of directly injecting fuel into the combustion chamber of the engine. Current fuel-injection technology mainly uses an injector located at the intake port of each cylinder. The injector sprays fuel into the port area while air, coming from the intake manifold of the engine, sweeps the fuel into the combustion chamber. Unlike typical fuel injection systems, a direct-injection system allows control over not just the amount of fuel entering the combustion chamber, but also when the fuel enters the combustion chamber. Direct injection can even control the shape of the fuel charge and thus create a cylinder charge having areas of pure air and areas of a combustible mixture. A benefit is an improved operating efficiency of the engine.
The direct-injected engines can suffer from reduced performance due to fuel vapor trapped in the fuel supply line to the engine. Fuel vapors in the line can occur, for example, upon start up of the vehicle. Fuel vapors can especially occur when the vehicle is started while the fuel is hot, for example, because the vehicle had previously been operating for shortly before startup. Thus, there is a need for a system and method that combine petrol engine performance with direct-injection efficiency, while maintaining low emission levels.
One way to reduce fuel vapors in a fuel line is to provide a fuel system that can increase the pressure of the fuel in the fuel lines. Continuous operation at the increased pressure, however, could reduce the life of pumps located within the fuel delivery system. Thus, a system and method are disclosed for operating the fuel system at an increased pressure when needed to reduce fuel vapors, and otherwise operating the system at a lower pressure.
According to one embodiment, fuel pressure in a fuel supply line can be regulated at different pressures. The fuel supply line delivers fuel from a fuel tank to a power source, such as a combustion engine. A fuel pump outlet line delivers fuel from the reservoir to a fuel supply line. An in-tank return line returns fuel from a fuel return line to the reservoir. A regulator connects with the fuel pump outlet line to maintain a pressure of the fuel pump outlet line at or below a pressure set-point of the regulator. A solenoid valve connects with the in-tank return line such that a set-point pressure of the regulator is utilized when the solenoid valve closes the in-tank return line.